The present invention relates to an expansion valve mounted to a refrigeration cycle of an air conditioner equipped for example in a vehicle, and especially relates to an expansion valve for automatically controlling the amount of refrigerant supplied to an evaporator in correspondence to the temperature of the refrigerant in a low-pressure refrigerant passage through which the refrigerant traveling from an evaporator toward a compressor travels.
A conventionally known expansion valve is equipped with a temperature sensing chamber that changes its pressure by sensing the change in refrigerant temperature traveling from an evaporator and through a low-pressure refrigerant passage toward a compressor, and a valve drive mechanism comprising a valve drive member and a valve means driven according to this pressure change in the temperature sensing chamber and thereby controlling the flow of the refrigerant traveling from the compressor toward the evaporator.
According however to this conventional expansion valve, a so-called hunting phenomenon sometimes occurs where the valve means opens and closes repeatedly.
Therefore, Japanese Patent Laid-Open Provisional Publication No. 5-322380 discloses filling an absorbing agent such as an activator to a hollow valve drive member and preventing such hunting phenomenon from occurring to the conventional expansion valve.
According to the above mentioned expansion valve disclosed in Japanese Patent Laid-Open Provisional Publication No. 5-322380, the overall structure of the expansion valve is rather complicated, utilizing for example a screw mechanism for fixing the power element portion constituting the temperature sensing chamber to the valve body. Thus, much cost is required for preparing the parts of the expansion valve and assembling the same.
Therefore, the present invention aims at providing an expansion valve having a simplified structure, by composing the expansion valve with a piping member and a cassette unit provided with all the functions of the expansion valve.
The expansion valve according to the present invention comprises a piping member including refrigerant passages to which pipes communicated with various equipments of the air conditioner are connected; a cassette unit inserted to the piping member, the cassette unit comprising a tube member formed integrally with a flange unit, a guide member, an orifice member, and a plate member fixed to the inside of the tube member, a valve means equipped inside a valve chamber defined by said orifice member, a plate member further defining said valve chamber, a spring disposed between the plate member and the valve means for biasing the valve means toward the orifice member, a shaft member for driving the valve means, a lid member welded onto the flange portion, a diaphragm pinched between the lid member and the flange portion and defining a gas charge chamber, and a stopper member having at the center thereof a tubed portion filled with absorbent for transmitting the displacement of the diaphragm to the shaft member; the expansion valve further comprising a ring for fixing to the piping member the lid member of the cassette unit inserted to the piping member; and a seal member disposed between the outer wall of the cassette unit and the inner wall of the piping member.
Further, the axis line of the refrigerant passage formed to the piping member is designed to correspond to the layout of the pipes.
Moreover, the present expansion valve can include a rubber bush equipped to the exterior of the tube member, and a rubber seal member baked onto the exterior of the tube member.
Even further, the guide member, the orifice member, and the plate member are fixed to the tube member through caulking.